Pyrolyzed biowastes deactivated potentially toxic metals and eliminated antibiotic resistant genes for healthy vegetable production

Lin Zhi; Rui Zhipeng; Liu Minglong; Bian Rongjun; Liu Xiaoyu; Lu Haifei; Cheng Kun; Zhang Xuhui; Zheng Jufeng; Li Lianqing; Drosos Marios; Joseph Stephen; Ishwaran Natarjan; Pan Genxing

doi:10.1016/j.jclepro.2020.124208

Pyrolyzed biowastes deactivated potentially toxic metals and eliminated antibiotic resistant genes for healthy vegetable production

J Clean Prod. 2020 Dec 10:276:124208. doi: 10.1016/j.jclepro.2020.124208. Epub 2020 Sep 19.

Authors

Lin Zhi^{1

2}, Rui Zhipeng^{1

2}, Liu Minglong^{1

2}, Bian Rongjun^{1

2

3}, Liu Xiaoyu^{1

2

3}, Lu Haifei^{1

2}, Cheng Kun^{1

2

3}, Zhang Xuhui^{1

2

3}, Zheng Jufeng^{1

2

3}, Li Lianqing^{1

2

3}, Drosos Marios^{1

2}, Joseph Stephen^{1

2}, Ishwaran Natarjan^{1

2}, Pan Genxing^{1

2

4}

Affiliations

¹ Institute of Resource, Ecosystem and Environment of Agriculture, and Department of Soil Science, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095, China.
² Center of Biomass Green Technology, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095, China.
³ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, 1 Weigang, Nanjing, 210095, China.
⁴ Key Laboratory of Recycling and Eco-treatment of Waste Biomass of Zhejiang Province, Zhejiang University of Science & Technology, Hangzhou, 310023, China.

Abstract

Potentially toxic metals (PTEs) and antibiotic resistance genes (ARGs) present in bio-wastes were the major environmental and health risks for soil use. If pyrolyzing bio-wastes into biochar could minimize such risks had not been elucidated. This study evaluated PTE pools, microbial and ARGs abundances of wheat straw (WS), swine manure (SM) and sewage sludge (SS) before and after pyrolysis, which were again tested for soil amendment at a 2% dosage in a pot experiment with a vegetable crop of pak choi (Brassica campestris L.). Pyrolysis led to PTEs concentration in biochars but reduced greatly their mobility, availability and migration potential, as revealed respectively by leaching, CaCl₂ extraction and risk assessment coding. In SM and SS after pyrolysis, gene abundance was removed by 4-5 orders for bacterial, by 2-3 orders for fungi and by 3-5 orders for total ARGs. With these material amended, PTEs available pool decreased by 25%-85% while all ARGs eliminated to background in the pot soil. Unlike a >50% yield decrease and a >30% quality decline with unpyrolyzed SM and SS, their biochars significantly increased biomass production and overall quality of pak choi grown in the amended soil. Comparatively, amendment of the biochars decreased plant PTEs content by 23-57% and greatly reduced health risk of pak choi, with total target hazard quotient values well below the guideline limit for subsistence diet by adult. Furthermore, biochar soil amendment enabled a synergic improvement on soil fertility, product quality, and biomass production as well as metal stabilization in the soil-plant system. Thus, biowastes pyrolysis and reuse in vegetable production could help build up a closed loop of production-waste-biochar-production, addressing not only circular economy but healthy food and climate nexus also and contributing to achieving the United Nations sustainable development goals.

Keywords: Antibiotic resistant genes; Bio-waste; Biochar; Clean production; Potentially toxic metals; Soil amendment; Vegetable production.